Apparatus for measuring low temperature stiffening of elastomers



Dec. 18, 1951 s. D. GEHMAN 2,579,424

APPARATUS FOR MEASURING LOW-TEMPERATURE STIFFENING 0F ELASTOMERS asheets-sheet 1 Filed June 8, 1948 INVENTOR.

SAMUEL D. GEHMAN FIG. I

ATTORNEY Dec. 18, 1951 5 D G H APPARATUS FORMMEASURING LOW-TEMPERATUSTIFFENING 0F ELASTOMERS Filed June 8, 1948 3 Sheets-Sheet 2 I N VENTOR.

SAMUEL D. GEHMAN ATTORNEY FIG. 3

Dec. 18, 1951 5. GEHMAN 2,579,424

APPARATUS FOR MEASURING LOW-TEMPERATURE STIFFENING 0F ELASTQMERS FiledJune a, 1948 3 Sheets-Sh'e'e't3 RESISTANCE 0 9a TIMER o c =0 G 54 ICEJUNCTION 96/ METER 93 I 94 I VENT QU JI v 90 TESTING UNIT FIG. .8DEHYDRATOR JNVENTOR. FlG. 9 SAMUEL D. GEHMAN By W ATTORNEY II has anoutwardly rolled flange portion l3 to. engage the shoulder l2 and toreceive the base' l4 and gasket i5 for suppot the calorirnf eter3.

A tube l6, preferably of metahgxtends through the wall of the pan I Iand the contai'iier i haying a seal ll therearound. The tube 16 iscoiled in the bottom of the pan ll (see Fig. 3) with the open end [8thereof extending vertically and 10- cated substantially centrally ofthe pan.-.; Air or other suitable gas is introduced to the tube 6emergingfromthe openfnd l8 and followingthe path.indica ted*the"arrows"in" Fig. 1 passes through thepor 't IS in the base l4j.f fThe base j l4 made'substantially in the form of a disc has 'ajcircular'recess preferably cut or formedloif .center'asshownto receive "an end ofthe calorimeter'3. The calorimeter'3 is of generally cylindrical formembodying aflbasje plate 2 l, a cap' 22,] and spaced inner and ou ter'walls 23 and 24,'res'pectively.'"' The base plate 2| and cap 22 areadvantageously for'm'edof' some suitable insulating "material such asMicarta and the like while the space between the walls '23 and 24 isfilled with somefibro'usinjsulating material25 such'asglass wool or'thelike and sealed by the ring ZBJ' TheSe meaSures serve to preventheatinfiltrationa'ndcold losses. n The compartment 21 formed in thecalorimeter 3 facilitates the freepassag'e therethrough of the air orgas emittedfrom the open end l8 of the tube [6. ,Thefair enters thec'ompartment 21' through an opening 2' 8 in"the basefplate' 2| whichisadapted to register with the port"! 9. in the base l4. The air;escapes-from compartment "2'! thm h 'ip it helsf i i the wall of thtubulansupporttfl' for the rack 31,, being discharged to theatmospherethrough the holef32 in the center of thef'capf 22 into which the end f fu pv 3 1 s rte -T Thecap "22;; as'preyio'usly stated; is ad'vantageously molded orcutfrom insulating material' and provided Witlra "1'i ng'33 of "cork-"or other similar material inserted ingroove 34 formedabout the'hole 32-;andon'the' under side of the cap. A plurality'of'holes -3 51'are'drilled in substantially equally spaced relationthrough the cap 22 and-the ring- 33. As'wi-ll be-s'eenfrom' Fig. 6, acorresponding number' of'lugs 36 are provided having 'st'em portions '37depending therefrom and extending through theholes '35 in the cap. 22'into .the compartment 121.:

The lowermost end of each of the stemgpor tions: 31 is: threaded ;as; at38 (see -;Fi;g-. 4); to receive the i er lamn m r 39.th ead t eme: onand ew' din P ace qaiam nu 40- .T e; clamp member Btlhas :a slottedportion ,4] havinga collar 42 thereon secured inplace by a screw 43. Avlower slottedlplamping member ,4! is inounted'on the 'rackj'3 Iis'fitted with, a collar 45 secured in' placebyfthe scr:ew"6. h e twodamping m b rs t 'iei d ii e erat s cu e the opposite endsofa samplestrip; 4'! of the ma; terial to be testediin a'manner to'be more fullydescribed hereinafterf' v r H I he n 22 i l m er aadily e-J movable tofacilitate the mounting of the several test pieces or sample strips 4!in the clamping members 39 and 44. A pair of knobs 58, as shown in Fig.6 of the drawings, enables the cap 22 to be easily inserted in orremoved from the upper end of the calorimeter 3. As will also be notedfrom Eig...6, .the,several sets of lugs 35..and associated clampingelements are convenientlyidentified by the numbers engraved or stampedadjacent each lug on the surface of the cap 22.

" For the sake of uniformity, all of the several test pieces or samplestrips 41 employed in the l testing of various elastomers are of uniformsize rand shape. The sample strips 47 are conveniently died'out oftensilete'st sheets and are 1.625 inches in length; .125 inch wide, and.079 inch thick.

, A suitable electrical heating element 55 is disposed in the hollowinterior of the tubular supporttil for the purpose of quickly effectinga 20 change in the temperature of the interior of the compartment 27 ofthe calorimeter 3. The electrical conductors'55 and 5| for connection toa suitable source of electrical power extend from the element 49 throughthe interior of the support 30 and out through hole 32. An opening 52 isprovided in thefcap 22 for the insertion of a theremocouple 51*], oneend of which extends downwardly into the compartment 27. A pair ofelectrical conductors 54 and 55 serve to connect the thermocouple 53into the operating circuit of the testing equipment in a manner to bedescribed in detail hereinafter,

@The yoke 5 on the testing unit 1 is formed with. a pair ofhorizontally'projectingparallel legs 56 and 57. The leg 56 of the yoke 5supports an index head 58 in rotatable relation thereon. The

index head 58 has a' centrally disposed vertically extending holetherein for the insertion of the uppermost end ofthe tubularflshield 59of the twisting means 60. A knurled headed screw 6| serves to adjustablysecure the shield 59 in the desiredivertical relation for the adjustmentof the twisting means 65. The screw 6| is disposed horizontally andthreaded into the outer periphcry of the index-head 58 so as to contactthe shield;

" 5E !lwli'e nthe latter is in place in the head.

The index head 58 has an arcuately formed cam surface; 62 of"approximately 180 degrees span for contact with the projectingnib 63 ofa microswitch*64. "The' microswitch" 64, provided with electricalconductors 65 and E5, is mounted upon" a'pl'ate 61 which issecured'to'theleg 56 ofthe yoke 5. A'vertically extending pin'lit in theleg' 56' of the yoke 5 serves as a stop to limit the extent of rotationof the index head 55 to the limits defined by the abutments'59 and l5 atthe extremities of the cam surface -62.

The twisting means 55 embodies a torsion wire H secured to the one endof the 'tubular shield 59 as shown'in'Fig. 4 of the drawings in such a'Wayfthat the wire is freely suspended therein.

The wire ll is secured at the opposite end to the shank; portion 12' ofa connector 73 which threaded as at '15 to receive the nuts l'S betweenWhich'is disposed the pointer 76. The lowermost endbf the twistingvmeans fifl'takes the form of a liead ll which is shaped as indicated inFig. 5 so as to interfit with each of the-several lugs 36 as s oc iat'edwitlr the calorimeter 3. A 'machine V straw-5191s inserted" through 'ahorizontally dis posed drilled hole in the head 1'! for threadedengagement" with a drilled and tapped hole in each of the lugs 36 whenthe head is interfitted therewithin turn.

The pointer TBo'f -the twisting means 6018 arran ed to sweep an arcuatescal such. its

example. s the adirstab emou tcd. profane... 19. The scale or protractorI9 is disposed h i; zontally :ior. shiitable'mov ment on a supportisurface 81.! havin a sli htly raise l ner fl n e inv to enable theprotractor to. be rotated: upon the. surface to. adjust the zero, pointvon thescale, to artinenosition ofhe pointer .16.. The. u per surface. oftheindexhead .58.. adiacentthe. cam surface 62 is. provided withaplurahtroi markings identified bythe referencecharacter 82 which are.arrangedtoregister with the. arrow head Sscribed on the end of theleg.56 .ofithe yoke 5. r The vertical axis of. the connector 131s ar;ranged to be. suspended by. thewirell and .the, shield v551 from theindexheadta in substantially. coincident relation withthecenter'pointofithe protractor 19 as will best be seen from -Eig. 2. The threadedportion M oftheconnector. 13. extends vertically downward throughtheregise tering apertures 84 and 85 in.the supportingsur;-. face 86 andthe leg .51 of the yoke, respectively. The entire twisting means--60 isfree tc-impart the desired torsionalstress upon thesample strip 41 whenthe connector 13 and the lug 36 are coupled together upon rotation ofthei-ndex head 58 to produce the result illustratedin-l igl 4 ofthedrawings. 1 The method of determining theeffectfof lowtemperatures onthe physical propertles-of--vari-- ous el'astomers will" bestbeunderstood by a detailed description of the operation ot-the'testingunit I and its associatedapparatus illustrated in Fig. 8 of thedrawings. 'f

To begin the testing operation, a supply-of; broken Dry Ice 86 isplaeedin'the' pan Tl of; the container 2 forming part of the"calorimeter 3. The cap 22 of the calorimeter 3 is-remoyed and aplurality of strips '41; "oispecifieddimen{ sions died out of elas'tomertes'tfsheet 'stoclgfthe torsion characteristics of which are to "be" infv'estigated at low; temperatures; are placed inthe testing unit I. Thepreferred'dimens'ions-of the strips 4! are 1.625 inches in length, 0.125Yineh wide, and 0.079 m n thick. The u'sflf 'the strips 4-! areinserted in: 'th "slotted cl mean 39am 44 a idterated. .1. as shown inFigs. fl and 4' .after which t :22 is replacedinthe "c grirn eter T 1 Thca rimeter i3, 15.. new. p aQ $1 nJD 1 Qn as i dicated n P e- 1 'othefcc a er and .1. tube is now slurrc ded'by Dry" ce 5 pan ll isconnected'tof, a suitablesupplyiof it. under a'slight. pressure. Aflexible hbsel 8 1 a Vantageously connectsjthe tube 1.6 t a .d drator 88which takes. the. former. a me, a s a uan it b acetone 'th e n purpose.of removing moisture from the" plied byhosef 89; thereby preventing.frost tion in the tube. The flexible hose.v videdwith an exhaust branch.96. hayin" able form'of adjustable yentoutletfqi The conductors 54 and55 forthe. therm eume 53 are connected with am ne:- var bl sistan'ceunit 92. through an ice. junctions} reie'rence' V setting up theapparatus. it. is ssfinfiial the. the portion of the.conductor'flwhichcom the. iron element of the. therm co 5 testing unit I and theiron ele em I t e t mocouple ot h wn in t e. s? s cti r $3. an ironwire. The. remainder. of the conduetor .4. settl n the. Gardenias ciarettes,- sass;

for the recording of temperatures.

Junc ion thermocouple-and the. res s ance un t. 9.2. can be'ordinarycopper. wire. The sam is true or the conductor .55 which, coupleszthe,resistance unit 92 and the Constantan element of the there. mocouple.53,.

The resistance unit 92 isadjusted by the use of some known standard,such as Dry Ice, the. temperature ofv which is 178.5. degrees 0., toenable. the millivoltmeter 9.4. whichis connected tothevariableresistance unit .92 by the 0011: ductors and 96 to readdirectly in degrees centigrade.

" 'Anadditional element of the complete appara-. we is an... audibletimer. unit 91 which has a standard" plug-11198 for insertion in aconven: tionalelectrical outlet. The timer- 91 is. con-1 trolled by theaction of the microswitch Gloom. nected to-thetimer bymeans of theconductors 65*and 66. The .timercircuit is normally :open, but is closedupon completion of the rotation of the index head-56 in a clockwisedirection through a full degrees. As the index head 58 reaches theend-of its rotation, the abutment 69 of the cam surface 62 depresses thenib.6-3 of the microswitch -64 and the timer circuit'ls closed. r

After the calorimeter 3 is in place in the recess 26 0f the base 14} itis necessary to rotate the calorimeter -bodily about its verticalaxis soas to bring the lug 36 associated with positionnum her I. on the cap 22into juxtaposition with the head-H. The yoke 5 is swung about asnecessary to bring the head 11 of the connector 13 into inter-fittingrelation to the lug- 36, whereupon the two elements are secured togetherby the'screws 18f With the twisting means 60 in its normal position ofrest and the elements all intercon nected, the protractor 19 iscarefully rotated in the horizontal plane to bring the zero markingthereon into juxtaposition with the'p'ointer T6. After all-theadjustments and connections indicated above-have been made, theapparatus is ready for use as soon as the temperature reading elementsindicate; that the desired temperature has been reached within thecompartment 21. It ordinarily desirable to begin the, tests at thelowest temperature and work upward in incre; merits o 5 t 10 esre s cding iarge 'u on the nature of the 'reacti'on of the particular ma:terial being checked. With the present appartus, it is possible toproduce temperatures in the compartment 21. as low as {590 degreescentig ader I Qnce the desired temperature. is reached in thecompartment 2.1, the apparatus is ready for the test of the firstspecimen. When the twistmg nieansffifl is at rest, the shoulder "it atone end of. thecam surface 62;.is against the pin168.. The techniciannot/grasps theindex head as and re; tates it through 180 degreesbr untiltherounded shoulder. 69 at the opposite extremityof the cam eras ilsqcsa s tea e 8 TM u t n al r theses? t m like P e 6, h s sr at e of. the.index. head 58}, the nib 63; of the micro..-

switch 64 will be: depressed bythe rounded snout. tier-69 of the camsurface 62 closing the circuit ,h these/itc isv disposed andinitiatingthe estat n fi er. 1 The timer 9:! is set to indicate thecompletion oifaftefn second. interval. At the endof the ten secondinterval, the technician takes note of the angular position ofthepointer i6 with. respect to the protractor 19. The maximum scale,read; is is n ed si ce manyi ec rrw e te w tbr cral andcause the pointerI6 to drift materially with respect to the scale in a relatively shorttime; The ten second interval insures the procureme'n ofmore reliableand uniform data. 4

At the conclusion of the ten secondinterval, the technician records theangle of twist as indicated by the pointer 16 on the protractor I9 andthe temperature reading. It will be noted that the mounting of thepointer I6 is such as will permit freedom of action of the pointer asthe index handis rotated- I It is desirable to have the scale reading onthe protractor. 19.fall within the range of .120 to 1'70 degrees. If thesample strip- 41 being. tested is quite soft, for example, therebycausing? the pointer to fall outside the prescribed ran e; it ispossible to adjust .theindex head 58 with relation to the shield 59 asby means of the screw GI so that the markings 82 will register withrefer ence to the arrow head 83. onthe leg 56 of the yoke 5, anavailable twist of less than 18.0 degrees, and will provide a means ofdetermining what number. of degrees less than a full rotation isrequired to bring the pointer 67 into the desired range. Alternatively,a pointer reading in the desired range may be obtained by the selectionof a torsion wire of suitable stillness.

Each individual lug 36 is, in turn, connected to each of the severalsample strips 4 and the data recorded for each one in turn. To this end,the calorimeter 3 is rotated bodily to'bring the lugs 36 intoregistrywith the head 1! of the twisting means 60. After each or" the.sample strips 41 has been tested atthe desired temperature, thetemperature of the compartment 21 is raised as desired by bleeding airout ofthe vent outlet ill or by the energization of the heater element49 or both. 7

The relative torsional modulus at any temperature is computed as theratio of the modulusat the low temperature in question to the modulus at25 degrees C. The modulus is connected with the twist measurement by therelation l89twist twist The apparatus requires a slight modification inthe nature of that illustrated in Figs. 9 to 12, inclusive, to enablerubber or plastic coated fabric to be tested. v

The calorimeter 3 is constructed, as before, with inner and outer walls23 and 24, respectively, between which an insulating material 25 isdisposed and sealed with the ring 26. The ring 26 supports a cap 95which is generally similar to the cap 22 of the apparatus of Fig. 1. Thecap 99 is provided with a single centrally disposed lug I like theseveral lugs 36 of the embodiment of Fig. 1 for demountable connectionModulus; o:

to the head TI of the connector 13 forming part of the twisting means60.

The lug I00 has a shank portion WI and a clamping portion I02 formedintegrally there with. The lowermost extremity of the clamping portionI02 is threaded as at I03 for the mounting of the weight I04 whichserves to retain the unit in proper vertical alignment in thecompartment 21 of the calorimeter 3. The fabric sample I05 is secured tothe clamping portion I02 by means of the plate' I06 held in place by thescrews I01 threaded into the clamping portion I02 being insulated fromcontact with the metal parts by means of the cork insulating pads I00(see Figs. 11 and 12).

As in thecase of the sample strips 41, it is desirable that the fabrictest pieces or samples I00 8 conform to a standard To this end, thefabric samples employed are 1 inch wide by 2 /2 inches long. I 1

The flexing of the fabric sample I05 upon rota tion of the lug I 00 isachieved by the studs I09 and I I0 which are fixedly mounted on theunder side of the cap so .as to project downwardly into the compartment21 of the calorimeter '3. The studs I09 and H0 are threaded into thecap-99 andlare coextensive in over-all length with the fabric sampleI05. The cap is provided with several drill holes III extendingtherethrough to serve as vents for the air passing into the base of thecompartment 21 from the tube I6 of the testunit- I when the severalparts are fitted together. The thermocouple IIZ extends through asuitable hole in the cap 99 so as to register the temperature of the.air? in'the compartment 21.

, Although the above-described structures represent. thepreferredembodiments of .the invention, it will be understood that other,modifica-, tions than those illustrated may be made in the apparatuswithout departing from the spirit or scope of the invention.

One of the distinct advantages of the use of the flexible torsion memberor wire II in the twisting means 60 is the fact that the testing unit Iis thereby enabled to indicate wide variations in modulus of theelastomers being tested. It is frequently found that the torsion modulusof elastomers will vary in range as much as 500 to 1000 times over thenorm when thematerials are subjected to extremely low temperatures. Nofixed application of force is required; in the apparatus of theinvention, in spite of the wide ranges covered, by reason of the factthat the'wire automatically compensates for oradlusts the torque appliedto the sample. I

While in accordancewith the patent statutes the best known embodimentsof the invention have been illustrated and described in detail, it is tobe particularly understood that the invention is not limited thereto orthereby, but that the inventive scope is defined'in the appended claims.p V I claim:

1. Apparatus for measuring low temperature stiffening of elastomerscomprising an enclosure; aremo'vable' cover'fo'r' the enclosure; asupport-. ing means suspended from the cover internallyof theenclosure;aplurallty of stationary clamping means on'the' supporting means; anumber of rotatable clamping means corresponding to' that, of thestationary clamping means extendi n'g throughthecover, each of saidstationary and rotatable clamping means being adapted to supporttherebetween a sample of the material to be tested; means producing acontrolled pre determined temperature within the enclosure; twistingmeans externally of the enclosure for disengageable attachment to therotatable clamping means; a flexible torsion member in the twistingmeans; and means externally of the enclosure and coacting with thetwisting means for indicating the relative degree of twist. imparted'bythe twisting means through the torsion member tothesample. "12.Apparatus for measuring low temperature stifiening of elastomerscomprisin means for supporting a sample of the material to be tested;aninsulated enclosure embodying a compartment encompassing thesupporting means; means directing fluid through the compartment; meansfor subjecting the fluid to controlled predetermined temperatureconditions; twisting mean's disposed externally 0f the enclosure "forimparting a twist to the sample while it is supported by the supportingmeans; a flexible torsion member in the twisting means for absorbing aportion of the twist to which the sample is subjected; and meansexternally of the enclosure for indicating the extent of twist effectedin the sample by the twisting means.

3. Apparatus for measuring low temperature stiffening of elastomerscomprising means for supporting each of a plurality of samples of thematerial to be tested; means enclosing'the supporting means forsubjecting all of the samples to controlled predetermined temperatureconditions; twisting means disposed externally of the enclosing meansfor rotating each of the supporting means; a flexible torsion memberbetween thetwisting means and the supporting 1; means; and meansexternally of the enclosing means coacting with the twisting means forindicating the extent of twist effected in the sample by the twistingmeans.

4. Apparatus for measuring low temperature stiffening of elastomerscomprising an enclosure; means in said enclosure for supporting a sampleof the material to be tested from opposed endsi gg thereof, one of saidsupporting means being fixed, and the other rotatable; twisting meansexter f nally of the enclosure; a flexible torsion means between thetwisting means and the rotatable I 1 supportin means; a scale externallyof the enclosure; means on the torsion member for in: dieating on thescale the twist effected in the sample; and means for varying thetemperature; of the enclosure over a wide predetermined range}, oftemperatures.

5. Apparatus for measuring low temperature stiflening of elastomerscomprising an enclosure} a removable cover for the enclosure; supportingmeans on the cover for disposition within the enclosure when the coveris in place; a first clamping means secured to the supporting means anda second clamping means extending through the cover for supportingtherebetween a sample of the material to be tested; twisting meansexternally of the enclosure for efiecting a partial rotation of thesecond clamping means to impart a twist to the sample; a flexibletorsion member in the twisting means for absorbing a part of the Iaction of the twisting means; and means s'up-'- ported by the flexibletorsion member for indi eating the relative torque induced in the sampleby the twisting means; and means varying the internal temperature of theenclosure. 6. Apparatus for measuring low temperature stiifening ofelastomers comprising an enclosure forming a compartment therewithin;clamping" means in the compartment for suspending from its opposite endsa sample of the material to be tested; means externally of the enclosurefor turning one of the clamping means and introducing a torsionaldeformation in the sample; means varying the temperature of the samplethrough a plurality of predetermined stage flexible torsion means in theturning means; absorbing a portion of torsional deformationiln; partedby the turning means; a scale externally of the enclosure; and meanssupported by th e flexible torsion means for indicating on the scale theeflective twist imparted to the sample by the turning means.

stiffening of elastomers comprising an enclosure;

a removable cover for the enclosure; mounting means on the cover for;disposition within the enclosure when the cover is in place; two sets ofclamping means, one set of which is secured to the mounting means whilethe other set is rotatably mounted in the cover for supportingtherebetween a plurality of samples of material to be tested; twistingmeans disposed externally of the enclosure, said twisting meansembodying a flexible torsion member and a disengageable connection foreach of the sets of rotatably mounted clamping means; a scale externallyof the enclosure; means connected to the torsion memher for indicatingon the scale the twist imparted to the sample bythe actuation of theftwisting means; means vv for directing a flow of =fluid through theenclosure; and means for sub- Jecting the fiuidto a widerange ofpredetermined temperature before it is introduced to the enclosure.

8 Apparatus for measuring low temperature stiffening of elastomerscomprising an enclosure; a supporting means in the enclosure forsecuring each end of a sample of the material to be tested; twistingmeans externally of the enclosure; a flexible torsion member between thetwisting means and one of the supporting means; means supported by thetorsion member externally oi the enclosure for indicating the degree oftwist effected in the sample by the twisting means; and means in theenclosure for subjecting the sample while so supported to a wide rangeof predetermined temperatures.

9. Apparatus for measuring low temperature stiffening of elastomerscomprising an enclosure; a supporting means in the enclosure forsecuring each end of a sample of the material to be tested; twistingmeans externally of the enclosure; means for attachment to'one of thesupporting means and the twisting means for absorbing a portion of thetorsional deformation imparted to the sample by the twisting means;means supported by the absorbingmember externally of the enclosure forindicating the degree of twist effected in the sample by the twistingmeans; and means for subjecting the'sample while supported in theenclosure to a'wide range of predetermined temperatures.

SAMUEL D. GEHMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PA'I'EN'I'S Germany}; Feb. 25, 1898

